Gap mapping for fitting composite doublers

Abstract

A non-conductive composite doubler is fabricated for application to an electrically conductive surface of a structure by: forming the composite doubler; placing an array of capacitive gap thickness sensors between the doubler and the structure surface; measuring the gap thickness between the doubler and the structure surface in a plurality of areas over the surface of the structure; using the gap thickness measurements to shape a layer of adhesive to essentially match the contour of the structure surface; and, applying the layer of adhesive to the doubler.

1. A method of mapping gap thicknesses between a first electrical conductor surface and a second electrical non-conductor surface, comprising:
 placing an array of capacitive gap thickness sensors between a structure providing the first electrical conductor surface and a composite doubler providing the second electrical non-conductor surface; 
 the gap thickness sensors being incorporated in a blanket including a first flexible layer of dielectric material against the first electrical conductor surface and a second flexible layer of dielectric material, the array of capacitive gap thickness sensors being between the first and second layers; 
 placing a third layer of electrical conductor material between the second layer and the second electrical non-conductor surface of the composite doubler; 
 sensing the thickness of a respective gap between the first and second surfaces at each of a plurality of locations using a respective capacitive gap thickness sensor of the sensor array, said thickness of a respective gap sensed in an area surrounding said respective gap; 
 collecting signals from the sensor array representing the measured gap thicknesses; and 
 using the collected signals to generate a data file representing a two-dimensional array of gap thickness values. 
 
     
     
       2. The method of  claim 1 , further comprising the step of:
 using the measured gap thicknesses to shape a layer of adhesive to substantially match a contour of the first surface; and 
 applying the shaped layer of adhesive to the first surface. 
 
     
     
       3. The method of  claim 1 , further comprising:
 multiplexing a plurality of electrical power signals; and 
 driving the capacitive gap thickness sensors using the multiplexed power signals. 
 
     
     
       4. The method of  claim 1 , wherein the structure comprises a component of an aircraft. 
     
     
       5. The method of  claim 1 , further comprising removing the sensor array from between the first and second surfaces. 
     
     
       6. The method of  claim 1 , further comprising:
 generating a numerical control (NC) program using the measured gap thicknesses; 
 using the NC program to control a NC cutter; and 
 cutting a shape of a layer of adhesive using the NC cutter. 
 
     
     
       7. An apparatus for mapping gap thicknesses between a first electrically conductive surface and a second electrically non-conductive surface, comprising:
 an array of capacitive gap thickness sensors in a blanket including a first flexible layer of dielectric material configured to be placed against the first electrically conductive surface and a second flexible layer of dielectric material, the array of capacitive gap thickness sensors being between the first and second layers; 
 a composite doubler including the second electrically non-conductive surface, the blanket being between the first electrically conductive surface and the second electrically non-conductive surface; 
 a third layer of electrically conductive material between the second layer and the second electrically non-conductive surface of the composite doubler; 
 the sensor array being configured to sense the thickness of a respective gap between the first and second surfaces at each of a plurality of locations using a respective capacitive gap thickness sensor of the sensor array at a respective location of the plurality of locations; and 
 a processor coupled with the sensor array, the processor being configured to receive signals collected from the sensor array representing the measured gap thicknesses and to use the collected signals to generate a data file representing a two-dimensional array of gap thickness values. 
 
     
     
       8. The apparatus of  claim 7 , wherein the conductive third layer is adhered to the blanket. 
     
     
       9. The apparatus of  claim 7 , wherein the conductive third layer is adhered to the composite doubler. 
     
     
       10. The apparatus of  claim 7 , wherein individual gap thickness sensors comprise an electrical coil and the sensor array comprises more than four gap thickness sensors. 
     
     
       11. The apparatus of  claim 7 , further comprising a multiplexer configured to multiplex the signals produced by the sensor array. 
     
     
       12. The apparatus of  claim 7 , further comprising an image processing program configured for use by the processor to generate a two-dimensional map of the gap thickness values. 
     
     
       13. The apparatus of  claim 7 , further comprising a controller configured to use the data file to control a numerical control (NC) cutter further configured to cut a shape of a layer of adhesive. 
     
     
       14. An apparatus for mapping gap thicknesses between a first electrically conductive surface and a second surface, comprising:
 an array of first capacitor plates between a first layer of dielectric material and a second layer of dielectric material, the first layer being configured to be placed against the first electrically conductive surface; 
 a composite doubler including the second surface, the first and second layers being between the first electrically conductive surface and the second surface; 
 a third layer of electrically conductive material in contact with the second surface of the composite doubler, the third layer being configured to operate as a second capacitor plate; 
 the array of first capacitor plates and the second capacitor plate being configured to sense the thickness of a respective gap between the first and second surfaces at each of a plurality of locations using a respective first capacitor plate of the array at a respective location of the plurality of locations; and 
 a processor coupled with the plate array, the processor being configured to receive signals collected from the plate array representing the measured gap thicknesses and to use the collected signals to generate a two-dimensional array of gap thickness values. 
 
     
     
       15. The apparatus of  claim 14 , wherein the conductive third layer is between the dielectric second layer and the second surface of the composite doubler. 
     
     
       16. The apparatus of  claim 14 , wherein the conductive third layer comprises conductive fibers of the composite doubler and forms the second surface. 
     
     
       17. The apparatus of  claim 14 , wherein individual first capacitor plates comprise an electrical coil and the plate array comprises more than four first capacitor plates. 
     
     
       18. The apparatus of  claim 14 , further comprising a multiplexer configured to multiplex the signals produced by the plate array. 
     
     
       19. The apparatus of  claim 14 , further comprising an image processing program configured for use by the processor to generate a two-dimensional map of the gap thickness values. 
     
     
       20. The apparatus of  claim 14 , further comprising a controller configured to use the gap thickness values to control a numerical control (NC) cutter further configured to cut a shape of a layer of adhesive. 
     
     
       21. A method of mapping gap thicknesses between a first electrically conductive surface and a second surface, comprising:
 placing an array of first capacitor plates between a structure providing the first electrically conductive surface and a composite doubler providing the second surface; 
 the first capacitor plates being between a first layer of dielectric material and a second layer of dielectric material, the first layer being against the first electrically conductive surface; 
 placing a third layer of electrically conductive material in contact with the second surface of the composite doubler, the third layer being configured to operate as a second capacitor plate; 
 sensing the thickness of a respective gap between the first and second surfaces at each of a plurality of locations using a respective first capacitor plate of the array at a respective location of the plurality of locations; 
 collecting signals from the plate array representing the measured gap thicknesses; and 
 using the collected signals to generate a two-dimensional array of gap thickness values. 
 
     
     
       22. The method of  claim 21 , wherein the collected signals are used to generate a data file representing the two-dimensional array of gap thickness values and further comprising:
 using the measured gap thicknesses to shape a layer of adhesive to substantially match a contour of the first surface; and 
 applying the shaped layer of adhesive to the first surface. 
 
     
     
       23. The method of  claim 21 , further comprising:
 multiplexing a plurality of electrical power signals; and 
 driving the first capacitor plates using the multiplexed power signals. 
 
     
     
       24. The method of  claim 21 , wherein the structure comprises a component of an aircraft. 
     
     
       25. The method of  claim 21 , further comprising removing the sensor array from between the first and second surfaces.